A measles epidemic controlled by immunisation

AIM: In 1997, an immunisation campaign, using measles-mumps-rubella vaccine, was planned for children aged 2-10 years to prevent a measles epidemic predicted by mathematical modelling. The epidemic started before the campaign and is described here. METHOD: Measles hospitalisation, notification and laboratory data were combined. RESULTS: The epidemic started in April 1997 and was largely over by January 1998. No deaths were identified and only one hospitalisation was coded as measles encephalitis, compared to seven deaths and ten cases of measles encephalitis in the 1991 epidemic. For the 12 months from 1 March 1997 there were 2,169 (60 per 100,000) measles cases identified, 314 (9 per 100,000) of whom were hospitalised. Two-thirds of hospitalised cases were notified. The age-standardised measles incidence rates were 33, 34, and 174 per 100,000 for Europeans, Maori and Pacific people, respectively. The respective age-standardised hospitalisation rates were 4, 9 and 32 per 100,000. Measles incidence was highest for under one-year-olds (904 per 100,000) and low for 11-16 year-olds (27 per 100,000)--the cohort previously offered a second vaccine dose. Most cases were aged 10 years and under, and this group were the main drivers of virus transmission. CONCLUSIONS: The immunisation campaign prevented 90-95% of predicted cases. The campaign was appropriately targeted at children aged 10 years and under.